I think the implication of that line was that Childs, although apparently 'consumed' by The Thing, was either somehow still present, or at least left his mark on the creature (If you remember, Childs used the term "Rapist" earlier on). It's alluded to throughout the story - when The Thing takes someone over, does the person have some influence in return? If you consider the tone of that final line and compare it to how the alien phrases itself throughout the rest of the story, it's completely out of character.